Heat exchanger tube support and spacing structure



N. D. ROMANOS Jan. 7, 1969 HEAT EXCHANGER TUBE SUPPORT AND SPACINGSTRUCTURE Filed April 25', 1967 Z of sheet INVENTOR. A//c//o/.As P.EOMANOS Mdm? ,4 TroeNEy Jan. 7, 1969 N. D. RoMANos HEAT EXCHANGER TUBESUPPORT AND SPACING STRUCTURE Filed April 25, 1967 sheet 3 ors INVENTOR.A//cf/a/.As Q QOMANQS ArrozA/EY United State-s Patent O 4 Claims Int.Cl. F2811 1/04 ABSTRACT F THE DISCLOSURE A tube support structure forpositively spacing and providing anti-vibration support for heatexchanger tubes arranged in a tube bundle. Tube spa-cer struts aredisposed in two, axially spaced and angularly related layers extendingbetween adjacent rows of tubes. The tube spacer strut layers aresupported in axially spaced relation by means of strut support beamsthat are arranged in a grid-like fashion on periodic spacing through theplane of support, thereby resulting in a less expensive tube supportstructure that provides an increase in available fluid ow area throughthe plane of support.

Background of the invention In heat exchangers of the shell and tubetype it is customary to arrange the tubes, which are long, thin-Walledmembers, in closely spaced relation in the form of a tube bundle. Axialsupport of the tube bundle is normally obtained by attaching the ends ofthe tubes to a tube sheet. In many applications the fluid velocitiespresent in the primary fiuid, lusually conducted by the tubes, and thesecondary fiuid, in which the tube bundle is immersed, gave rise to asignificant amount of vibration that can be potentially dangerous toheat exchanger operation in that it can be the cause of tube failure.Vibrations within the apparatus can also occur as a result of externalshock loading. In such applications means must be employed to laterallysupport the tubes so as to reduce the eitects of these vibrations. Suchmeans have commonly taken the form of spacing devices which po-sitivelyseparate adjacent tubes in the tube bundle such that they cannot contacteach other as a result of the vibration present in the heat exchanger.

Several structural arrangements have been proposed to perform thisfunction. One type involves a plurality of apertured plates which areaxially spaced within the tube bundle extending laterally thereof. Theplates contain one of these groups of apertures through which the tubesof the tube bundle extend and another group which permits axial fiow ofsecondary fluid. A second type of tube support employs a plurality ofrelatively thin spacer bars that extend between adjacent rows of tubes.The bars are disposed in two groups which intersect one another and areconnected at their intersections so as to form a gridlike structure.This type of tube support is commonly referred to as an egg cratesupport.

Each lof these types of lateral tube support arrangements suffers fromcertain manifest disadvantages. In both arrangements the amount ofavailable fiow area through the plane of support is considerably reducedsuch that high pressure losses are experienced in the secondary fluidfiowing through the heat exchanger. Moreover, the cost of constructingeach of these types of tube supports is relatively expensive. Theapertured plate form of support requires the provision of severalthousand apertures either by drilling or stamping to accommodate thelarge number of tubes present in tube bundles employed for high capacityheat exchangers and another several thousand drilled or stampedapertures to accommodate secondary Huid flow through the support. Theegg crate type' of support, while providing somewhat more available flowarea through the plane of support than does the apertured platearrangement, nonetheless creates creates a certain amount of pressureloss in the secondary fluid flowing through t-he support. This form ofsupport s also expensive due to the fact that milled slotsl must beprovided in all the spacer bars so that the bars of each lgroup can bemutually connected at their points of intersection.

Summary of the invention A principal object of the present invention isto provide inexpensive means for positively spacing each of the tubes ina tube bundle in a manner that will lminimize the effect of systemVibration on the tubes, yet, at the same time, will reduce the amount ofpressure loss suffered by the secondary fluid in flowing through theplane of support. This objective is obtained by employing a grid-likestructure formed of two groups of strut support beams that areinterconnected at their intersections in conventional egg crate fashionbut which are disposed on periodic spacing through the tube bundleinstead of between each adjacent tube row as is presently theconvention. These beams are slotted on one edge, one group being slottedalong its top edge and the other along its bottom edge so as to receivetwo groups of tube spacer struts which extend through the spacesIbetween the intermediate tube rows and which are axially spaced 4fromone another by a dimension approximating the height of the strut supportbeams.

Because the two groups of tube spacer struts are axially spaced from oneanother on each plane of support, the amount of available Huid flow areathrough the tube support struts is significantly increased. Thisresults, therefore, in a proportionate reduction in the amount ofpressure loss experienced by the secondary fiuid in flowing through thetube support structure. Additionally, fabrication costs of the presentarrangement are considerably reduced as compared with those required fora conventional egg crate tube support structure where all of the tubespacer members must be provided with machined slots to permit theirinterconnection at each intersection. In the present novel apparatusonly the strut support `beams need be slotted and, since they aredisposed on a periodic spacing between every tenth or so adjacent tuberows, their number represents only a fraction of that which requiresmachining in a conventional arrangement. The tube spacer struts whichcomprise the majority of the tube spacer members in the arrangement canbe formed of simple rod or bar stock and require no machining. Thus theamount of total machining, and thereby the cost re'- quired to fabricatethe structure, is materially reduced.

Description of the drawings FIGURE 5 is a section taken along line `5--5of FIG- URE 2.

Description of the preferred embodiment Referring to the drawings thereis shown in FIGURE 1 a heat exchanger 10 in the form of a substantiallycon'- ventional shell and tube type vapor generator-embodying theinvention. The heat exchanger 10 comprises averti',- cally arrangedshell 12 defining an evaporation Vchamber 14 and a vapor dome 16. In theevaporation chamber 14 is located a tube bundle 18 comprising aplurality of U-shaped tubes 20. The lower end of the tube bundle 18 isvertically supported by means of a tube sheet 22 wherein tube seats 24are provided to receive the ends of the tubes 20 and to place them influid communication with the inlet and outlet compartments 26 and 28,respectively, of the primary lluid manifold section 30 of the vaporgenerator. The tube bundle 18 includes a plurality of long, closelyspaced U-tubes 20 which are disposed in lparallel rows with theirarcuately-formed end portions 32 concentrically arranged, so that theinnermost end portions are of relatively small radius and the outermostend portions are lof relatively large radius, with the remainingintermediate end portions being of progressively graduated radii. Sincethe tube bundle 18 conforms to the cylindrical shape of the evaporationchamber 14, more tubes 20 are provided in the central tube rows and therows of tubes radially removed from the central rows have a graduallydecreasing number of tubes. The disposition of the tubes in this mannerleads to a regular tube pattern within the tube bundle comprising thetube rows and intermediate intersecting lanes or spaces. The angles atwhich the lanes intersect is determined by the distance between tubesand the tubular pitch.

Surrounding the periphery of the tube bundle 18 is a generallycylindrical baffle member 34 that is concentrically spaced from the wallof the shell 12 to form, on its interior, the evaporation chamber- 14and, about its exterior, an `annular fluid passage 36. As shown inFIGURE 1 the bottom end of the baille 34 is vertically spaced from thetube sheet 22 in order to establish fluid communication between thepassage 36 and the evaporation chamber 14. Thus, secondary liquidadmitted to the vapor generator by an appropriate nozzle (not shown)communicating with the interior of the shell 12. is caused to flow downthe annular passage 36 and thence to the evaporation chamber 14 where itforms a body of liquid therein that immerses the tube bundle 18.

In operation, when hot primary fluid is passed through Y the tubes 20 ofthe tube bundle 18 by circulation of the fluid through the inlet andoutlet compartments 26 and 28 of the primary fluid manifold 31 andsecondary liquid is introduced to the evaporation chamber 14 from thefeedwater inlet nozzle a transfer of heat is effected from the primarylluid to the secondary liquid. This transfer to heat results in thetransformation of some of the liquid to vapor which rises from theevaporation chamber 14 to the vapor dome 16 and is removed therefrom byappropriate means (not shown). The transfer of heat from the primaryfluid to the secondary liquid also creates, by means of thermal siphonicaction, a circulation of secondary liquid through the liquid body. Flowof the more dense, cooler secondary liquid occurs in a downwarddirection through the annular passage 36 and, of the heated, less denseliquid upwardly through the evaporation chamber 14.

The flow of primary fluid through the tubes 20 and the circulation ofsecondary liquid through the vessel is at a sufllciently high velocityas to have the tendency to create vibrations within the unit. Vibrationsmay also occur as a result of external shock loading of the unit which,together with the internal vibrations of the system, have a potentiallydeleterious effect on the tubes. Therefore, in order to prevent oralleviate the adverse effects of these vi-brations on the tubes 20 anumber of lateral support structures indicated as 40 in FIGURE l arepositioned within the heat exchanger at axially spaced positionstherealong.

According to the invention each of the support structures 40 comprisesan annular frame that embraces the periphery of the tube bundle 18,being formed by a pair of axially spaced rings 42. The rings 42 attachtwo groups of structural members indicated as strut support beams 44aand 44b which are straight, elongated bars disposed laterally betweenopposite portions of the rings 42 and attached at their ends as by meansof welding. The beams 44a and 44b are periodically spaced and arrangedso as to extend on edge along lanes defined between adjacent tube rowsthrough the bundle. Disposition of the beams between every tenth ortwelfth tube row has been found to -be adequate in most cases, but thisof course may vary according to the size of the tubes employed in thetube bundle and the amount of vibration experienced within the heatexchanger. As shown, the beams 44a of one group cross those 44b of theother group at an angle determined by the arrangement of tubes 20`within the tube bundle 18 so as to form a grid-like structure.

All of the strut support beams 44a and 44b are identically formed asshown in FIGURE 4 with two sets of slots 46 and 48 cut into one sideedge. Slots 46 are cut to a depth approximately midway through the beamsand are spaced apart a distance equal to that corresponding to thenumber of tube rows between the beams in the arrangement illustrated.These slots 46 function to effect locking interconnection of beams 44aand 44b at their intersections. Slots 48, on the other hand, are adaptedto mount a number of tube support struts 50 and are therefore cut onlyto the depth necessary to secure these struts. The slots are disposed ona spacing that corresponds to the lateral spacing between adjacent tuberows in the tube bundle 18.

In fabricating the tube support structure the beams 44a are arrangedwith the slots 46 and 48 disposed along the upper edge and the beams 44bwith the comparable slots disposed along their lower edge. The slots 46in the respective beams are arranged so as to oppose one another andeach beam is then secured by forcing it into the slots 46 in the other,thereby resulting in a grid-like structure wherein the upper side edgeof the beams in one group and those along the lower edge of the othergroup are slotted. Thereafter, tube support struts 50 which are alsoarranged in two groups, indicated as 50a and 50b, are mounted in theedges of the respective strut support beams in the slots 48. The struts50 may be formed of straight bars having a lateral dimension whichcorresponds to that of the spacing between adjacent tube rows. As shownin FIGURE 3 of the drawings, the struts 50a extend parallel to the strutsupport beams 44b and are mounted in slots 48 on the upper edge of thebeams 44a. The struts 50h extend parallel to the beams 44a and aremounted in slots 48 on the lower edge of the beams 44b. The assembly iscompleted by attaching the rings 42 to the ends of the beams 44 andstruts 50 as by means of welding. The rings 42 are axially spaced,therefore, by means of the ends of the strut support beams 44. Thestruts 50a are welded to the underside edge of the upper ring 42 whilethe struts 5011 are attached to the upper side edge of the lower ring.

With reference to FIGURES l and 5 of the drawing, each of the tubesupport structures 40 can be mounted in axially spaced locations alongthe length of the tube bundle by appropriate attachment to the innersurface of the annular baffle 34. According to the preferred embodimentsuch attachment is obtained by providing bracket members 52 weldedly orotherwise secured to the baille 34 and adapted to vertically supporteach of the support structures 40 by engaging the lower ring 42.

By providing anti-vibration tube support apparatus according to thepresent novel arrangement several particularly advantageous results areobtained. First, because the tube spacer struts and the strut supportbeams are formed with a lateral dimension that corresponds to thespacing between adjacent rows of tubes the tubes are positively spacedfrom one another and thereby rendered less affected by vibrations thatoccur within the heat exchanger. Secondly, because the majority of thetube spacing members are constructed of struts formed from simple barstock and require no machining, the only machining required is thatnecessary to provide slots in the strut support beams which compriseonly about $40 of the tube spacing members. This, therefore, results ina proportionate reduction in the cost of machining required to fabricatethe apparatus. Thirdly, because the tube support struts are arranged ingroups that are axially spaced from one another and therefore do notintersect at the plane of support, there is provided approximately 30%more ilow area through the tube suport structure at each plane ofsupport. This increase in available llow area results in =aproportionate reduction in the amount of pressure loss experienced bythe secondary liquid in flowing through each tube support structure.

It will be understood that various changes in the details, materials andarrangements of parts which have been herein described and illustratedin order to explain the nature of the invention, may be made by thoseskilled in the =art Within the principle and scope of the invention asexpressed in the appended claims.

What is claimed is:

1. Anti-vibration support aparatus for positively spacing a plurality oftubes arranged in a tube bundle, said tubes extending parallel to theaxis of said tube bundle and being disposed in a regular pattern of tuberows spaced by sets of intersecting lanes comprising:

(a) means forming a frame embracing the periphery of said tube bundle;

(b) a plurality of spacer struts extending along lanes 'between adjacenttube rows and having their ends attached to opposite portions of saidframe, said spacer struts being arranged in a pair of axially spaced,angularly disposed layers of parallel struts, the struts of one of saidlayers extending through one set of lanes and the struts of said otherlayer extending through said intersecting lanes; and

(c) means for supporting said spacer strut layers in axially spacedrelation, said means including:

(i) a plurality of strut support beams arranged in a pair of angularlyrelated groups 0f parallel beams, the beams of one group extending alongperiodically spaced lanes in one of said sets of lanes and the beams insaid other group extending along periodically spaced lanes in said setof intersecting lanes;

(ii) means for attaching the ends of said beams to opposite portions ofsaid frame; and

(iii) means on the beam of each group for mounting the struts of therespective spacer strut layers.

2. Apparatus as recited in claim 1 including means for connecting saidgroups of beams in intersecting relation.

3. Apparatus as recited in claim 2 wherein all of said beams areidentically formed and including:

(a) a -rst set of slots formed along one edge thereof for mounting saidtube spacer struts;

(b) and a second set of slots formed along one edge thereof forconnecting said groups of beams in intersecting relation.

4. Apparatus as recited in claim 3 wherein said rst and second sets ofslots are formed on the same edge of said beams.

References Cited UNITED STATES PATENTS 1,882,474 10/ 1932 Black 165-1621,946,234 2/ 1934 Price 165-162 1,967,961 7/ 1934 Metten 165--162FOREIGN PATENTS 878,232 9/ 1961 Great Britain. 962,011 6/ 1964 GreatBritain.

35 ROBERT A. -OLEARY, Primary Examiner.

MANUEL A. ANTONAKAS, Assistant Examiner.

